Why do you want an LED screen? There's been all sorts of trouble with them. Stripes, weird lighting, half of the screen with a cast on it. Loads of threads about this.
When they're working, they look great and they improve battery life. Look, the MacBook Pro got them in 2007 and the MacBook Air got them in January. With time comes improvements. LED screens are part of Apple's promise to become a Greener Apple and eventually ALL computers will use them or a similar technology. I expect to see them.